An input buffer may be utilized for connection of an input/output (I/O) system to another system, device, or component. In modern electronics, buffers will generally include integrated circuits (ICs). As integrated circuit process technology has advanced to higher densities, the feature size of transistors has been reduced, thus enabling system operations at low voltages and high speeds and providing for high-density device layout. Another result of reduced feature size that can cause complications is the reduction in gate oxide voltage tolerance in thinner oxide devices. With the reduction in voltage tolerance, higher voltages may damage input/output circuits that are designed for low voltage, thus limiting the range of applications for circuit components.
However, certain conventional I/O standards may require that a system be interfaced with external voltages that are higher than the internal voltages used within the system. Thus, it may be necessary to interface a system utilizing low-voltage transistors to high voltage systems, thereby posing a challenge in I/O system design.
In a conventional input buffer, the buffer circuit may be constructed with high voltage components. When the buffer circuit is deactivated, the input transistors of a conventional system may be capable of tolerating higher voltages. However, such voltage support is provided at the expense of adequate performance. Among the issues regarding the operation of an I/O system are the headroom and the duty cycle for a signal. Headroom is a limitation on a transferred signal, representing the amount of additional signal above the nominal input level that can be sent into or out of an electronic device before distortion occurs. Duty cycle represents the ratio between the length of a signal pulse to the signal period, with a signal presenting a perfect square wave, with a signal length equal to one-half of the period, has a duty cycle of 0.5 or 50%. In higher voltage operation, a conventional I/O system will provide low headroom, a poor duty cycle, and high power dissipation.